SENSITIZED FLUORESCENCE IN VAPORS OF ALKALI METALS: III. ENERGY TRANSFER IN CESIUM–CESIUM COLLISIONS

Abstract

Collisions of the second kind leading to the transfer of excitation between 6 2P1/2 and 6 2P3/2 states in cesium have been investigated by studying sensitized fluorescence in cesium vapor at pressures in the range 2 × 10−6 to 7 × 10−5 mm Hg, which were not accessible previously to such experiments and at which trapping of resonance radiation is virtually absent. The use of an improved fluorescence tube and of high-resolution interference filters in conjunction with a liquid-air-cooled photomultipler tube permitted accurate measurements of extremely low fluorescent light intensities. The total cross sections for the processes 6 2P1/2 → 6 2P3/2 and 6 2P1/2 ← 6 2P3/2 equal 0.64 × 10−15 cm2 and 3.1 × 10−15 cm2 respectively and are in a ratio of 0.20, which agrees well with the value predicted by the principle of detailed balancing.